Read the assertion and reason carefully to mark the correct option.
Assertion: An aircraft flies along the meridian, the potential at the ends of its wings will be the same.
Reason: Whenever there is change in the magnetic flux e.m.f. induces.

Options

A. If both assertion and reason are true and reason is the correct explanation of assertion
B. If both assertion and reason are true but reason is not the correct explanation of assertion.
C. If assertion is true but reason is false.
D. If assertion is false but reason is true.

Explanation

To analyze the assertion and reason provided in the question, we can break down the solution into clear steps:

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that when an aircraft flies along the meridian, the potential at the ends of its wings will be the same.
- This implies that there is no difference in electric potential between the two ends of the wings.

2. **Understanding the Reason**:
- The reason states that whenever there is a change in magnetic flux, an electromotive force (e.m.f.) is induced.
- This is based on Faraday's law of electromagnetic induction, which indicates that a changing magnetic field can induce an e.m.f. in a conductor.

3. **Analyzing the Aircraft's Motion**:
- When the aircraft is flying along the meridian, it is moving through the Earth's magnetic field.
- The Earth's magnetic field has both horizontal and vertical components. The horizontal component is directed towards the meridian.

4. **Effect of Magnetic Field on the Aircraft**:
- The horizontal component of the magnetic field does not induce an e.m.f. because it is parallel to the direction of the aircraft's motion.
- However, the vertical component of the magnetic field, which is directed towards the center of the Earth, can induce an e.m.f. as it is perpendicular to the motion of the aircraft.

5. **Conclusion on the Assertion**:
- Since the vertical component of the magnetic field can induce an e.m.f. across the wings of the aircraft, the potential at the ends of the wings will not be the same.
- Therefore, the assertion is **false**.

6. **Conclusion on the Reason**:
- The reason is **true** because it accurately describes the phenomenon of electromagnetic induction as per Faraday's law.

7. **Final Answer**:
- Since the assertion is false and the reason is true, the correct option is **Option 4**.